Cardiovascular System; Regulation and Electrical Activity Flashcards
What do Chest Compression do in terms of Blood Perfusion?
You push on the heart to pump the blood and then let the heart to refill. This maintains blood perfusion pressure to at least the heart and brain. (Chest compressions only meet 30% of normal heart function)
What happens when you stop Chest compressions in terms of Blood Perfusion?
Perfusion dramatically drops so should be limited to 5 seconds to shock patient and after will take a few pumps to get back to normal perfusion pressure
In terms of Cardiac Output how is Heart Rate Regulated?
When blood vol decreases and stroke vol decreases AAR heart rate will increase to increase cardiac output and maintain BP as…(CO=SVxHR). This is caused by neural stimulation (para/sympathetic NS) or endocrine activity e.g. adrenaline
What happens in Vascular Action? (Initial regulation of BP)
- Cells respond to ischaemic (low O2) conditions by releasing CO2, lactic acid and other metabolites
- Results in Vasodilation of arteries
- And so, promotes blood flow and O2 delivery to ischaemic tissue
- Also helps meet tissues nutritional demand
What is Peripheral Resistance?
Opposition to blood flow through peripheral vessels, mostly determined by lumen size
How is Peripheral Resistance Regulated?
By sympathetic NS - constriction/dilation of arteries or hormone release. Control centre is ‘vasomotor centre VCM’ which determines ‘vasomotor tone’ (aka lumen)
VCM Negative Feedback System
- VCM receives information from sensory receptors
- Chemoreceptors see if higher CO2 conc
- Responds by increasing heart rate/respiration rate
- AND/OR baroreceptors see if lowered BP
- Responds by vasodilation/increased heart rate
2 Ways to Increase Blood return to Heart
- Muscular contractions of calf muscles aids venous return against gravity
- Inspiration also helps draw blood back towards the heart
Pathway of Electricity in the Heart
- Group of cells called the sinoatrial node (SAN) located in the right atrium stimulate the release of an electrical impulse. This causes the contraction of the atria
- The wave of excitation travels to the atrioventricular node (AVN) located in the bundle of his, in the septum
- The AVN causes electricity then travels along the bundle of his (septum) to the Purkinje tissue at the bottom and upwards across the ventricles causing the ventricles to contract
How is Heart Rate Controlled electrically?
The autonomic NS (parasympathetic and sympathetic). The SAN acts as a pacemaker for heart rate. And the brain will send signals to para to slow down heart rate and the symp to speed up heart rate.
Limb Lead Plaacements
Red= right arm/shoulder Yellow= left arm/shoulder Green= left ankle Black= right ankle (earth) Anagram - Ride, Your, Green, Bicycle
Limb Lead view; 1st three
View generated is called the Eindhoven’s triangle and generates 6 views on the vertical plane. The first 3 views (I, II, III) are the combination of R→L, R→F and L→F
Limb lead view; last 3
aVL, aVR, aVF; the diagonal lines across to the heart on 2nd diagram
Chest Leads Dot Placement Steps
- Identify ‘Angle of Louis’ on Sternum
- The 2nd intercostal space is just to the right
- Go to the 4th intercostal space three rib spaces down
- The 1st dot is placed on the left of 4th intercostal space while 2nd dot goes on right
- The 4th dot goes on the 5th intercostal space in the midclavicular line
- The 3rd dot is placed between the 2nd and 4th
- The 6th dot is placed on the same line as the 4th but mid-axillary line (under armpit)
- The 5th dot is placed between dots 4 & 6
Chest Leads Views
Shows the horizontal (transverse) plane giving 12 views.
